“It is difficult for even well-funded opposition to deny the House of Representatives the opportunity to vote on a bill that has 68 percent of the House as co-sponsors, and overwhelming support from veterinary groups and horse organizations in every state,” Whitfield said.

But as lobbying on the bill grows more intense, with new allegations about the influence of campaign contributions, at least one congressional expert says the number of co-sponsors — although attention-getting — far from guarantees action.

In the House it remains bottled up in the Energy and Commerce Committee, where Rep. Marsha Blackburn, R-Brentwood, an opponent, is vice chair. In the Senate it has passed committee but has yet to get a floor vote. The office of Senate Majority Leader Harry Reid, D-Nev., declined to comment.

Blackburn maintains that she’s simply defending an iconic Tennessee business that’s under attack.

“We want to save a Tennessee industry that has a 97 percent compliance rate and protect these animals from the bad actors who make up the 3 percent on noncompliance,” Blackburn spokesman Mike Reynard said. “Unfortunately, those on the other side have refused to come together and work with us in finding a solution that would eliminate bad actors. Instead, their only focus has been to simply eliminate the walking horse industry altogether.”

Because of the August congressional recess, fewer than 30 legislative days remain before the November elections.

Widely seen as cruel, soring involves using caustic chemicals, chains, special pads and other devices on a walking horse’s legs and hooves to produce an artificially high step, referred to as the “Big Lick.” Whitfield’s bill would outlaw the use of “action devices” and fund a significant increase in Department of Agriculture inspectors to police horse shows.

With 114 of its House sponsors Republicans, “we are approaching having a majority of the majority on board,” said Keith Dane of the Humane Society of the United States.

He was referring to an unwritten House rule coined a decade ago by former House Speaker Dennis Hastert, R-Ill., who said he wouldn’t bring a bill to the floor unless a majority of Republicans backed it.

Currently, there are 234 Republicans in the House, 199 Democrats and two vacancies. The 114 Republican co-sponsors fall four short of the number needed to qualify under Hastert’s rule.

While the Hastert rule still exists, House Speaker John Boehner “uses it very judiciously lest he foment a broader revolt within his conference,” said Sarah Binder, an expert on congressional politics at the Brookings Institution.

She said one key to whether the PAST Act will get a vote is going to be “whether there are rival measures supported by House Republicans that would need to be considered as well.”

One such bill comes from Blackburn, who opposes the PAST Act. Her bill calls for scientific testing to detect soring but has no restrictions against action devices. Blackburn contends it adds all the strength needed to the Horse Protection Act of 1970, the original legislation against soring.

Clant M. Seay, an Oxford, Miss., attorney and member of the All-American Walking Horse Alliance, which favors the PAST Act, says “confirmed walking horse industry participants” have given at least $25,000 to Blackburn’s 2014 re-election campaign.

In an interview, Seay called Blackburn “a shill for the Big Lick crowd.”

Reynard said Blackburn “got involved in this issue because an iconic and uniquely Tennessee brand was under attack from a liberal left-wing organization.”

PAST Act supporters continue to see Steve Smith, campaign finance chairman to Republican Sen. Lamar Alexander and a donor to Blackburn, as another “obstructionist,” said Teresa Bippen, who represents a group called Friends of Sound Horses.

Smith is president of the Tennessee Walking Horse Breeders and Exhibitors Association, which fiercely opposes the bill.

Seay says Smith and other PAST Act opponents have given tens of thousands of dollars this year and in past elections to key Senate Republicans, including Alexander and Senate Minority Leader Mitch McConnell, a Kentucky Republican. Like Blackburn, Alexander and McConnell have a competing bill criticized by PAST Act supporters.

“Its’s a shame Senator Alexander has lent his good name and reputation to people who champion horse soring,” Seay said.

But contributions and lobbying by Smith have had no effect on Alexander, said spokesman Brian Reisinger, who added the senator wants only “to end soring while preserving the Tennessee Walking Horse tradition.”

Smith himself said, “I haven’t been to Washington lobbying anyone.”

Meanwhile, PAST Act opponents point to the role of Whitfield’s wife, Connie, as a senior policy adviser to the Humane Society.

On its website, the American Horse Council says that despite the large number of co-sponsors, the bill “still needs more help from the horse community at large to get it over the finish line.” James J. Hickey Jr., president of the group, said the council is contacting affiliated groups nationwide to continue their grass-roots lobbying of Congress.

Bippen said, “We believe the will of the people will prevail and the PAST Act will come to a vote.”

Reach Paul C. Barton at pbarton@gannett.com and on Twitter @PaulCBarton.

Competing legislation

Whitfield’s bill would:

• Outlaw the use of “action devices” such as chains or pads and fund a significant increase in Department of Agriculture inspectors, paid for with assessments on horse show managers.